Another intriguing property was discovery of the magnetisation spontaneously arising in the superconducting state revealed by the Kerr rotation of polarization of light reflected from the crystal surface in \((b,c)\)  plane [1]}. In the orthorhombic materials the symmetry does not allow the direct transition from normal to magnetic superconducting state. Hence, the appearance of magnetism must be result of additional phase transition from initial nonmagnetic superconducting state to more complex magnetic one. Indeed, the phase transition splitting was revealed in some experiments [1]}, [3]}, [4]}. At same time on the other specimens at ambient pressure there was observed only single phase transition [5]}, [6]}, [7]}, but the splitting was appeared above about 2 Kbar [8]}.
